Sorghum bicolor (L.) Moench. - Grain sorghum
Taxonomic position:Family: Poaceae Barnhart; genus: Sorghum Moench.; species: Sorghum bicolor (L.) Moench. (Cherepanov, 1995).
The most common sorghum classification in the Russian Federation has been elaborated by the N.I. Vavilov All-Union Research Institute for Plant Cultivation and includes the following sorghum varieties: Guinean grain sorghum - S. guineense (Stapf.) Jakuschev.; Bantu grain sorghum - S. bantuorum Jakuschev.; durrha - S. durra (Forsk) Jakuschev., it has three subspecies: Ethiopian durrha - S. durra ssp. aethiopicum Jakuschev.; Nubian durrha - S. durra ssp. nubicum Jakuschev.; Arabian durrha - S. durra ssp. arabicum Jakuschev.; Chinese sorghum or kaoliang - S.chinense Jakuschev.; sweet or fodder sorghum - S. saccharatum Jakuschev.; broomcorn or industrial-grade sorghum - S. technicus (Koern) Roshev.; grass sorghum or Sudan grass - S. sudanense (Piper.). S. almum P. was first cultivated a relatively short time ago (in the 1950s); it is a perennial rhizome plant used as green fodder, for silage and as a pasture crop.
Biology and Morphology:2n=20. Sorghum is an annual and perennial herbaceous plant. It has fibrous roots which deeply penetrate soil. Sorghum stalk is 75-250 cm tall, with varied thickness (1-2.5 cm) and a dry, semi-dry or juicy marrow. Some varieties, especially Sudan grass, tend to tillering with lateral shoots, which may be as high as the main stalk. The number of leaves varies from 8 to 20. Sometimes sorghum leaves are up to 1 m long. Leaf surface may be smooth or crimped to various degrees. Sorghum inflorescence is a panicle of different shapes and lengths, usually 10-40 cm long, with broomcorn 50-60 cm long. The panicle's main axis (the rhachilla) may be absent, as long as the panicle itself, or of an intermediate length. The panicle's rhachilla is straight, curved or drooping. The panicle's pedicel may be shorter than the upper leaf's sheath or the same length. Sometimes 10-30 cm of the pedicel protrude from the sheath. On the tip of each panicle's branch, there is a pair of spikelets. The lower one is sessile, bisexual and fruit-bearing, while the upper one is male and sterile. Each bisexual spikelet usually has two flowers. One of them is rudimentary. Therefore, the caryopsis develops from the upper flower. The male spikelet is single-flowered. Spikelet glumes may be pubescent or bare, short, medium or long and ranging from closely adhering to widely open. When ripe, spikelet glumes occur in many different colors. They may become straw-colored, olive green, brick red, red, purple, violet, chestnut colored or black. Sorghum fruit is a round caryopsis without a furrow. The caryopsis is bare or tunicate when the flower and spikelet glumes closely adhere to it but are not concrescent with it. Sorghum grains may be differently colored: white, gray, brown or black. 1,000 grains weigh 20-30 g.
Ecology:Sorghum is a spring, heat-loving, drought-resistant and salt-tolerant crop. Usually simultaneous sprouts appear on the 8th to 10th day after planting when the soil heats up to 13-15°C. Optimal seed germination temperature is 20-30°C. Effective heat sum (above 10°C) for fast-ripening varieties is 2000-2500°C, 3000-3500°C for mid-season varieties, and over 3500°C for slow-ripening varieties. Sorghum resists not only soil but air droughts. Despite its drought-resistibility, sorghum readily reacts to irrigation. Sorghum is suitable for cultivation on saline soils, as it tolerates salt concentrations of up to 0.6-0.8%. Sorghum is not particularly fastidious about soil but does not thrive in acidic soils. It adapts easily to different types of soil. A very valuable biological feature of sorghum lies in the ability of most sorghum varieties' stalks and leaves to remain green until full kernel maturity. Sorghum is a short-day crop. It thrives with 10-11 hours of sunlight a day. A shorter photoperiod results in a vegetation period 3 weeks longer prior to flowering and almost 6 weeks longer prior to full flowering. Many sorghum varieties do not flower at all with insufficient light. Fast-ripening varieties' vegetation period lasts 90-105 days; mid-season varieties' vegetation period lasts 106-120 days; and slow-ripening varieties' vegetation period lasts 120-130 days or more. Sorghum is an autogamous plant prone to cross-pollination, which, depending on the particular variety, takes place 3.3-16.6% of the time. The plant blossoms after 1-5 days upon its panicle's emergence. First to blossom are the spikelets in its upper part. Gradually, this process spreads to lower sprigs. Anthers and stigmae issue from the open flowers almost simultaneously. Ripe anthers burst, the pollen spills out, resulting in cross-pollination. Each flower blossoms for 1-2 hours, and the whole panicle blossoms for 10-13 days. Sorghum flowers usually open in the early morning hours. Sorghum blossoms most actively when air temperatures reach 16-18°C and relative humidity reaches 60-80%. With higher temperatures and normal humidity, sorghum blossoms more slowly and sometimes stops blossoming altogether. Lower air temperatures, precipitation the day before or at night, abundant dew and overcast weather also delay panicle flowering. Sorghum pollen begins to germinate immediately upon falling on the stigma. Sorghum pollen is viable for up to 5 hours. The stigmae are ready for fecundation 1-2 days prior to flowering and remain viable for 10-14 days. Heterosis with sorghum is more pronounced than with maize.
Distribution:Sorghum is cultivated all over the world on 70-75 million hectares. Only wheat, rice, maize and barley are cultivated more widely. Sorghum is grown mostly in Asia (49-50%) and in Africa (32-33%), while in America its share is 15%, and in Australia and Europe, it is only 2-3%. Grain sorghum is the most common variety (it is cultivated on about 60 million hectares). Other groups of economically valuable sorghum varieties are cultivated mostly in Australia, in the southern Africa, in Argentina, in the USA and in some European countries. In the Russian Federation, sorghum is cultivated in relatively arid zones of Northern Caucasia, the Volga Region and the Far East. In 2004, 28 varieties of cereal sorghum were approved for cultivation in various areas of the Russian Federation (Aist, Volgar, Volgogradskoye 20, Volzhskoye 4, Zersta 90, Kamyshinskoye 75, Knyazhna, Luchistoye, Orion, Start, and others), as were 21 varieties of sweet sorghum (A 63, Volzhskoye 51, Kamyshinskoye 7, Kinelskoye 3, and others) and 7 varieties of broomcorn sorghum (Dekorativnoye, Kinelskoye 67, Priusadebnoye, and others). Breeding agencies include the Altai Research Institute for Agriculture, the Stavropol Research Institute for Agriculture, the Research Institute for Agriculture of the Lower Volga, the P.M. Konstantinov Research Institute for Breeding and Seed-Farming of the Volga Region, the Southeastern Research Institute for Agriculture, the Russian Research Institute for Sorghum and Maize, and the All-Union Research Institute for Sorghum and Other Cereal Crops. Sorghum has been cultivated since the 3rd or 4th millennium B.C. Originally, sorghum was from Northeastern Africa (Ethiopia and the Sudan). For many centuries, sorghum has been exceptionally important in Africa and Southeastern Asia, especially in India, mostly as a cereal crop. As an exceptionally drought-resistant plant, sorghum provoked interest in the USA and in Southern Europe only in the 20th century. Sorghum quickly replaced maize in Kansas, Nebraska, Texas and other states where maize cannot resist droughts and yields less.
Economic value:Sorghum is a universal crop used for production of all the main fodder types: grain, silage, herbage, hay and haylage. Each sorghum seed contains 70-75% starch, 12-13% protein and 3.5% fat (1 kg of sorghum grain is the equivalent of 1.3 fodder units, while 1 kg of silage is the equivalent of 0.24 fodder units). Sorghum is processed to obtain cereals, flour, and starch. Sorghum protein.s content of indispensable amino acids is poorly balanced. Among them, the greatest biological value lies in lysine and methionine. Sorghum protein contains 1.81-2.49% lysine and 1.22-1.97% methionine. There are specimens with high protein contents (up to 19.3%) and a balanced amino acid composition that contain more than 3% of lysine. Sorghum straw is used to manufacture paper, wicker goods and brooms. Sorghum is a tilled crop. It is used as a post-harvest, post-cut and a mixed crop (together with soy and haricot). Sorghum's best precursors are leguminous plants, winter and spring spiked crops, potatoes, silage cabbage, annual grasses (except Sudan grass) and perennial grasses harvested for hay. Sorghum readily reacts to fertilizer application. 100-140 kg of NPK are applied per hectare. In addition, 40,000 kg of manure may be applied per hectare for sweet sorghum. Sorghum is sown in wide rows. The seeds are planted at depths of 4-6 cm. 40,000-120,000 sorghum plants are cultivated per hectare. Grain sorghum is gathered by two-phase harvesting or direct combining. Sorghum yields 2,500-3,000 kg of grain and 30,000-40,000 kg of herbage per hectare.
References:Cherepanov S.K. 1995. Vascular Plants of Russia and Neighboring Countries. St. Petersburg, p. 762.
Konovalov Y.B., ed. 1990. Particular Breeding of Field Crops. Moscow, pp. 140-153.
Malinovsky B.N. 1992. Sorghum in Northern Caucasia. Rostov-on-Don, p. 208.
State Register Breeding Achievements Approved for Practical Application. 2004. Moscow, pp. 29-30.
Zhukovsky P.M. 1971. Cultivated Plants and Their Congeners. Leningrad, pp. 130-139.